Examples of methods that have been employed in the prior art for rot-proofing and termite-proofing structural wooden materials include (1) injection into the trunks of standing trees, (2) chemical treatment of the cut ends of felled timber, (3) coating and spraying lumber with chemicals, (4) immersing lumber in chemicals, and (5) injecting chemicals into lumber under pressure.
The method involving injection into the trunks of standing trees is an easy method, but it has poor treatment efficiency since considerable time is required to inject a large amount of chemical in treating individual trees, and the chemical used must be soluble in water. Thus, this method is hardly used at all at present.
Height difference injection methods are typically used for treating the cut ends of felled timber with chemicals. Examples of such methods include the Bushley method, in which the cross-sectional surfaces of the bases of bark-covered logs are coupled with a chemical tank installed at a high location immediately after felling followed by the injection of chemical utilizing the water pressure resulting from this height difference, and a method in which, after peeling the bark for a distance of about 10 cm from the base of bark-covered logs, the peeled base is covered with one end of a tire tube and fastened to the log with wire or a rubber band, after which chemical is injected into the tube from the other end and the base of the log is inclined at a steep angle and allowed to stand undisturbed. These methods are also hardly used for the same reasons as the aforementioned method involving injection into the trunks of standing trees.
Methods involving coating or spraying lumber with chemicals are the most common methods of rot-proofing and termite-proofing treatment, and are routinely employed at building construction sites. In these methods, an emulsion or wettable powder containing rot-proofing and termite-proofing ingredients is diluted with water, a chemical in which the termite-proofing ingredient is diluted with kerosene is applied to the lumber with a brush, or the chemical is sprayed onto the lumber with a sprayer. However, these methods have the shortcomings of requiring considerable time and trouble for treatment, the surfaces to which the chemical adheres are extremely limited to unevenness of coating or spraying, and the chemical being unable to be adequately impregnated into the lumber, thereby making lumber susceptible to infiltration by putrefying microorganisms and termite from those sections where the chemical has not adhered or only adhered in a small amount. In addition, there is also the problem of environmental contamination since the chemical sprays onto lumber other than the lumber targeted for spraying.
Although the method involving immersing lumber in a chemical allows the chemical to be more reliably impregnated into the lumber than the aforementioned coating or spraying, it has the shortcomings of requiring the providing of a large immersion tank and a large volume of chemical so that the lumber to be treated can be completely immersed.
Although methods involving the injection of a chemical into lumber under pressure enable chemicals to reliably penetrate inside the lumber in a short period of time, they also have the shortcomings of requiring a device to generate pressure, requiring a large amount of chemical in the same manner as immersion methods, and require measures for preventing pollution with respect to treating the waste chemical following treatment. Although CCA (chromium-copper-arsenic) compounds having both termite-proofing and rot-proofing effects have been used as chemicals in these methods, treatment using this method is decreasing rapidly for the reasons mentioned above.
As has been previously described, although there are numerous methods for termite-proofing treatment of lumber, since each of these methods have problems, treatment is performed by selecting the method thought to be optimum based on the respective situation. Among these, although injection into the trunks of standing trees provides a simple method that is easy to implement, since it requires the injection of a large amount of chemical and considerable time is required for that injection, it is currently hardly employed at all for reasons of poor treatment efficiency. However, it is thought that this method would proliferate considerably if an active ingredient or preparation were available that would enable treatment to be performed with a small amount of chemical and in a short period of time.